JP6895364B2 - Heat-dissipating paint composition, heat-dissipating coating and coating method - Google Patents

Description

The present invention relates to a heat-dissipating coating formed on the surface of a base material to promote heat dissipation, a heat-dissipating coating composition contained in the heat-dissipating coating, and a film-forming method.

A heat-dissipating coating formed on the surface of the device is known to promote heat dissipation of the device. The heat-dissipating coating generally contains a base material made of a resin such as an acrylic resin and a heat-dissipating filler made of inorganic particles such as carbon black held by the base material (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-281514

The conventional heat-dissipating coating has a heat-dissipating filler as an essential configuration. Therefore, it is necessary to select a heat-dissipating filler suitable for the base material, prepare the heat-dissipating filler, and disperse the heat-dissipating filler in the base material. In addition, some heat-dissipating fillers accelerate the deterioration of the base material. If the heat-dissipating filler can be omitted, the heat-dissipating coating can be easily produced.

In view of the above background, it is an object of the present invention to provide a heat-dissipating coating composition, a heat-dissipating film, and a film-forming method capable of omitting a heat-dissipating filler.

ここで、Ｒ_１は水素又はメチル基であり、Ｒ_２は炭素数が５〜２０の直鎖アルキル基である。 In order to solve the above problems, the first aspect of the present invention is a heat-dissipating coating composition for forming a heat-dissipating film, which is a poly-α-olefin and silane represented by the following chemical formula (1). A heat-dissipating paint composition comprising a coupling agent.

Here, R ₁ is a hydrogen or methyl group, and R ₂ is a linear alkyl group having 5 to 20 carbon atoms.

According to this aspect, it is possible to provide a heat-dissipating coating composition in which the heat-dissipating filler can be omitted. The linear alkyl group is flexible and can have various conformations. Therefore, due to molecular motion including rotation and vibration of the side chain composed of linear alkyl groups, energy consumption in the side chain increases, contact between the side chain and external gas molecules and liquid molecules increases, and heat dissipation is promoted. It is thought that.

Further, in the above embodiment, the content of the silane coupling agent is preferably 1 to 10 wt% with respect to the total of the poly-α-olefin and the silane coupling agent.

According to this aspect, the reaction rate between the poly-α-olefin and the silane coupling agent is improved.

Further, in the above embodiment, R ₂ of the chemical formula (1) is preferably a linear alkyl group having 10 to 15 carbon atoms.

According to this aspect, the heat dissipation performance of the heat dissipation film can be improved.

Another aspect of the present invention comprises the heat-dissipating coating composition according to the first and second aspects described above, and provides a heat-dissipating coating formed on the surface of a base material.

According to this aspect, it is possible to provide a heat-dissipating coating that can omit the heat-dissipating filler.

In the above embodiment, the thickness is preferably 15 to 50 μm.

According to this aspect, the heat dissipation of the heat dissipation coating can be improved. In the heat-dissipating coating, heat is dissipated mainly through the side chain of the linear alkyl group located on the surface, so that the larger the surface area with respect to the volume, the better the heat-dissipating property.

In the above embodiment, the base material may be formed of a material containing aluminum.

According to this aspect, the heat-dissipating coating can be stably adhered to the base material.

In the above embodiment, the content of the heat-dissipating filler formed from the inorganic particles is preferably 0.1 wt% or less. Further, in the above aspect, it is preferable that the heat-dissipating film does not contain a heat-dissipating filler formed from inorganic particles.

According to this aspect, the heat dissipation of the heat dissipation coating can be improved. It is considered that the heat-dissipating filler inhibits the molecular motion of the linear alkyl group on the surface to reduce the heat-dissipating property.

ここで、Ｒ_１は水素又はメチル基であり、Ｒ_２は炭素数が５〜２０の直鎖アルキル基である。 Another aspect of the present invention is a film forming method for forming a film on the surface of a base material, wherein a solution containing the composition represented by the following chemical formula (1) and a silane coupling agent is used as a base. It is characterized by including a first step of applying to the surface of the material, and after the first step, a second step of heating the base material to which the solution is applied at 100 ° C. to 150 ° C.

Here, R ₁ is a hydrogen or methyl group, and R ₂ is a linear alkyl group having 5 to 20 carbon atoms.

According to the above configuration, it is possible to provide a heat-dissipating coating composition, a heat-dissipating coating, and a film-forming method capable of omitting the heat-dissipating filler.

Test container used for heat dissipation performance test In the heat dissipation performance test, (A) a graph showing the relationship between heat dissipation time and temperature, and (B) a graph showing the relationship between heat dissipation time and temperature difference (ln (Ts-Ta)). Graph showing the relationship between the thickness of the heat-dissipating coating and the heat-dissipating speed ratio Graph showing the relationship between the number of carbon atoms in the side chain of the heat-dissipating coating and the heat-dissipating speed ratio

Hereinafter, embodiments of a heat-dissipating coating composition, a heat-dissipating coating, and a coating-forming method according to the present invention will be described.

ここで、Ｒ_１は水素又はメチル基であり、Ｒ_２は炭素数が５〜２０の直鎖アルキル基である。 (Heat-dissipating paint composition)
The heat-dissipating coating composition according to the embodiment is a composition contained in the heat-dissipating coating film, and contains a poly-α-olefin represented by the following chemical formula (1) and a silane coupling agent.

Here, R ₁ is a hydrogen or methyl group, and R ₂ is a linear alkyl group having 5 to 20 carbon atoms.

The poly-α-olefin represented by the chemical formula (1) can be produced by a polymerization reaction of an α-olefin having 7 to 22 carbon atoms. _{Further, R 1} can be converted to a methyl group by using an α-olefin having a side chain of a methyl group at the β-position.

The silane coupling agent has a structure represented by the general formula _{X-Si-Y 3.} Here, X is an organic group, and Y is an alkoxy group having 1 to 3 carbon atoms. The organic group is, for example, a vinyl group, an epoxy group, a methacryl group, an acrylic group, an amino group, or a mercapto group. The alkoxy group is, for example, a methoxy group, an ethoxy group, a dimethoxy group, or a diethoxy group. An alkylene group having 1 to 6 carbon atoms may be interposed between X and Si. Further, Y may change one alkoxy group to a methyl group. The silane coupling agent includes, for example, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane. , 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-Methyloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxy Silane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane.

The content of the silane coupling agent is 1 to 10 wt%, more preferably 1 to 5 wt% with respect to the total of the poly-α-olefin and the silane coupling agent. When the silane coupling agent is vinyltrimethoxysilane, R _{1 of the} poly-α-olefin is hydrogen, and R ₂ is a linear alkyl group having 5 to 20 carbon atoms, the content of the silane coupling agent. When the content is 5 to 10 wt%, the reaction rate between the silane coupling agent and the poly-α-olefin is 90% or more, and when the content of the silane coupling agent is 1 to 4 wt%, the reaction rate is 98% or more. It was.

(Heat-dissipating paint)
The heat-dissipating coating material contains the heat-dissipating coating composition containing the above-mentioned poly-α-olefin and silane coupling agent and a solvent for dissolving the heat-dissipating coating composition, and is prepared as a liquid. The solvent is preferably a volatile organic solvent, for example, ketones such as acetone and methyl ethyl ketone, acetate esters such as methyl acetate, ethyl acetate and propyl acetate, and hydrocarbons such as normal hexane, cyclohexane, methylcyclohexane and normal heptane. It may be hydrogens, aromatic hydrocarbons such as toluene, xylene and benzene, and ethers such as butyl cellosolve, phenyl cellosolve and dimethyl cellosolve. The heat-dissipating paint may further contain a pigment, a pigment dispersant, a leveling agent, an antifoaming agent, a thickener and the like.

(Heat-dissipating coating)
The heat-dissipating coating is a coating formed on the surface of the base material, and includes the above-mentioned heat-dissipating coating composition. The base material may be, for example, a heat exchanger housing, a tube, or a core. The heat exchanger may be, for example, a vehicle intercooler or radiator. The base material may be formed of iron, aluminum, or an alloy thereof.

In the heat-dissipating film, the poly-α-olefin represented by the chemical formula (1) is bonded to the substrate via a silane coupling agent. In the silane coupling agent, the alkoxy group becomes a hydroxyl group by hydrolysis, and bonds to the base material by hydrogen bonding with the hydroxyl group on the surface of iron or aluminum. In addition, the silane coupling agent binds to the poly-α-olefin at the organic group. Silane coupling agent, for example, replaced with R ₂ of Formula (1), in an organic group is bonded to the carbon of the main chain of poly -α- olefin. The thickness of the heat-dissipating coating is preferably 15 μm to 50 μm.

The heat-dissipating coating has a content of a heat-dissipating filler formed from inorganic particles of 0.1 wt% or less. Further, it is preferable that the heat-dissipating coating does not contain a heat-dissipating filler formed of inorganic particles. Heat-dissipating fillers include, for example, carbon black, zinc oxide, aluminum nitride, silicon oxide, calcium fluoride, boron nitride, quartz, kaolin, aluminum hydroxide, bentonite, talc, salicite, forsterite, mica, cordierite, and boron nitride. Etc. particles.

The side chains of the linear alkyl groups of the poly-α-olefin that form the heat-dissipating film are flexible and can have various conformations. Therefore, due to molecular motion including rotation and vibration of the side chain, energy consumption in the side chain increases, contact between the side chain and external gas molecules and liquid molecules increases, and the heat dissipation of the heat-dissipating coating is improved. Conceivable. The side chain is preferably a linear alkyl group because of the ease of molecular motion. It is considered that if the side chain contains a polar functional group, a double bond, a triple bond, or the like, the molecular motion of the side chain is inhibited and the heat dissipation property is lowered.

(Film formation method)
In the first film forming method, the above heat-dissipating paint is applied to the surface of the base material in the first step. The coating method includes spray coating, dip coating, brush coating, roller coating and the like. In the next step, the base material coated with the heat-dissipating paint is heated at 100 to 150 ° C. for 20 to 40 minutes. By this step, the poly-α-olefin and the silane coupling agent are bonded and the solvent is volatilized. As a result, a heat-dissipating film is formed on the surface of the base material.

(Example of film forming method)
In the chemical formula (1), R ₁ was hydrogen and R ₂ was used as a heat-dissipating paint composition having various carbon numbers. The silane coupling agent was vinyltrimethoxysilane. The poly-α-olefin and the silane coupling agent were diluted with butyl cellosolve to obtain a heat-dissipating paint. The content of the silane coupling agent was 5 wt% with respect to the total of the poly-α-olefin and the silane coupling agent. The concentration of the poly-α-olefin and the silane coupling agent with respect to butyl cellosolve was 5 wt%. An aluminum plate (A1050, length 150 mm × width 70 mm × thickness 0.8 mm) was used as the substrate (base material). The heat-dissipating paint was applied to one surface of the substrate by spraying an appropriate amount of the heat-dissipating paint on one surface of the substrate by air spraying. Subsequently, using a heating furnace, the substrate coated with the heat-dissipating paint was heated at 120 ° C. for 30 minutes. Upon heating, the poly-α-olefin was bonded to the surface of the substrate via the silane coupling agent, the butyl cellosolve was volatilized, and a heat-dissipating film was formed on the surface of the substrate. The thickness of the heat-dissipating film after heating was defined as the thickness of the heat-dissipating film. The thickness of the heat-dissipating coating can be adjusted by the amount of the heat-dissipating paint sprayed by the air spray.

(Heat dissipation performance test)
The heat dissipation of the heat dissipation coating was evaluated by the following heat dissipation performance test. As shown in FIG. 1, the bottom of a rectangular parallelepiped steel can 1 (length 130 mm × width 50 mm × height 100 mm, thickness 0.8 mm) with the bottom cut off is closed with a substrate 3 on which a heat-dissipating coating 2 is formed. Test container 4 was prepared by. The substrate 3 was arranged so that the surface on which the heat-dissipating coating 2 was formed faced downward (outside). The steel can 1 and the substrate 3 were liquidtightly bonded by an adhesive. The upper part and the side part of the test container 4 are covered with Styrofoam 6 (insulation material) having a thickness of 30 mm. The test container 4 was placed on the table 7 via the styrofoam 6, and the substrate 3 was placed at a position sufficiently distant from other structures. A liquid inlet is formed in the upper part of the test container 4. Inside the test container 4, 350 mL of engine oil heated to 100 ° C. was charged at the start of the test. The charged engine oil was stirred at 200 rpm by a stirring rod 8 provided inside the test container. Further, a thermocouple 9 for measuring the temperature of the engine oil is provided inside the test container 4. Further, a thermocouple (not shown) for measuring the outside air temperature is provided on the outside of the measuring device (outside the styrofoam). The measurement was carried out in an environment where the outside air temperature was room temperature (about 22 ° C.), and when the temperature of the added engine oil decreased from 100 ° C. to 85 ° C., the time was set to 0, and the subsequent engine oil temperature was set to 0. Recorded. In addition, as a reference test, a similar heat dissipation performance test (temperature measurement) was performed using a test container having a substrate having no heat dissipation film at the bottom.

2 (A) and 2 (B) show the results obtained from the heat dissipation performance test. 2 (A) and 2 (B) use poly-α-olefins represented by the chemical formula (1) in which R ₁ is hydrogen and R ₂ has 13 carbon atoms, and the thickness of the heat-dissipating coating film is high. This is the result when the value is 20 μm. In the graph of FIG. 2A, the horizontal axis is time [s] and the vertical axis is temperature [° C.]. The temperature of engine oil decreases with the passage of time due to heat dissipation through the substrate. The graph of FIG. 2 (B) shows the result of FIG. 2 (A) converted. The horizontal axis is the time [s], and the vertical axis is the value obtained by subtracting the outside air temperature Ta from the engine oil temperature Ts. The number of natural bodies (ln (Ts-Ta)) is used. As can be seen from FIGS. 2A and 2B, it was confirmed that the slope of the graph was larger than when the bottom substrate had a heat-dissipating coating and when it did not have a heat-dissipating coating (reference test). The slope of the graph in FIG. 2B, that is, the amount of change in ln (Ts-Ta) per unit time (1s) is defined as heat dissipation rates Vs and Vr. Let Vs be the heat dissipation rate when the substrate has a heat dissipation film, and Vr be the heat dissipation rate when the substrate does not have a heat dissipation film (reference test). Further, the ratio of the heat dissipation rate Vs to the heat dissipation rate Vr in the reference test is defined as the heat dissipation rate ratio R (= (Vs−Vr) / Vr × 100).

(Effect of film thickness on heat dissipation)
_{By setting R 1 of the} poly-α-olefin represented by the chemical formula (1) to hydrogen and R ₂ to 13 carbon atoms and changing the amount of the heat-dissipating paint sprayed onto the substrate, heat-dissipating coatings of various film thicknesses are formed. Was formed. The thickness of the heat-dissipating coating produced was 15 μm, 45 μm, and 78 μm. A heat dissipation performance test was conducted on a substrate having a heat dissipation film having each of these film thicknesses.

FIG. 3 is a graph showing the relationship between the thickness of the heat-dissipating coating and the heat-dissipating speed ratio. From the results of FIG. 3, it was confirmed that the heat dissipation rate ratio decreased as the thickness of the heat dissipation film increased. Further, it was confirmed that the heat dissipation rate ratio hardly changed in the range where the thickness of the heat dissipation film was 80 μm or more. When the thickness of the heat-dissipating coating according to this example was 10 μm or less, it was difficult to form a homogeneous coating. Further, since the heat dissipation rate ratio is 0 when the thickness of the heat dissipation film is 0, it is preferable that the heat dissipation film has a thickness of at least 10 μm or more. Therefore, it can be said that the thickness of the heat-dissipating coating is preferably 15 to 50 μm. Further, in the range of this range, the thinner the film thickness, the better the heat dissipation. Therefore, the thickness of the heat dissipation film is more preferably 15 to 40 μm, further preferably 15 to 30 μm. The thinner the heat-dissipating coating, the greater the ratio of surface area to volume and the greater the ratio of linear alkyl groups placed on the surface of the heat-dissipating coating to volume. Therefore, it is considered that the heat dissipation property is increased.

(Effect of side chain on heat dissipation)
_{R 1 of the} poly-α-olefin represented by the chemical formula (1) was hydrogen, _{the carbon number of R 2} was 8, 13, and 17, and a heat-dissipating film having a thickness of 20 μm was formed. Then, a heat dissipation performance test was performed on each substrate.

FIG. 4 is a graph showing the relationship between the number of carbon atoms in the side chain and the heat dissipation rate ratio. From the results of FIG. 4, when the number of carbon atoms of the linear alkyl group (the number of carbon atoms in the side chain) is 8, 13, or 17, the heat dissipation rate ratio is larger than 0, and the case where the heat dissipation film is not provided. It was confirmed that the heat dissipation was improved. From the approximate curve based on the result of FIG. 4, it is considered that the heat dissipation rate ratio becomes larger than 0 in the range of 5 to 20 carbon atoms in the side chain, and the heat dissipation film improves the heat dissipation. It was confirmed that the heat dissipation rate ratio became maximum when the number of carbon atoms of the linear alkyl group (the number of carbon atoms in the side chain) was 10 to 15. Therefore, it can be said that the number of carbon atoms in the side chain is more preferably in the range of 10 to 15.

(Effect of heat-dissipating filler on heat-dissipating coating)
The heat-dissipating paint according to the examples was prepared by setting the carbon number _{of R 2} of the poly-α-olefin contained in the heat-dissipating paint composition to 13. Further, as a comparative example, a heat-dissipating paint in which carbon black (particle size 3 μm) was suspended at a concentration of 0.5 wt% was prepared as a heat-dissipating filler. The heat-dissipating paint according to the comparative example is the same as the heat-dissipating paint according to the examples except that it contains a heat-dissipating filler. Using the heat-dissipating paints according to Examples and Comparative Examples, heat-dissipating coatings having a thickness of 20 μm were formed. A heat dissipation performance test was performed on a substrate having a heat dissipation coating according to these Examples and Comparative Examples.

As a result of the heat dissipation performance test, it was confirmed that the heat-dissipating film (without heat-dissipating filler) according to the example had higher heat-dissipating property than the heat-dissipating film (with heat-dissipating filler) according to the comparative example. It is conceivable that the heat-dissipating filler is exposed on the surface of the heat-dissipating coating, so that the density of side chains composed of linear alkyl groups on the surface is reduced. Further, it is considered that the heat-dissipating filler inhibits the molecular motion of the side chain composed of the linear alkyl group on the surface of the heat-dissipating coating. As a result, it is considered that the heat-dissipating coating containing no heat-dissipating filler has improved heat-dissipating properties as compared with the heat-dissipating coating containing the heat-dissipating filler.

1: Steel can 2: Heat-dissipating coating 3: Substrate 4: Test container 6: Styrofoam 7: Stand 8: Stirring rod 9: Thermocouple

Claims (7)

A heat-dissipating paint composition for forming a heat-dissipating film.
Look including the following Formula poly -α- olefin and a silane coupling agent represented by (1),
_{R 2} of the chemical formula (1) is a linear alkyl group having 10 to 15 carbon atoms.
A heat-dissipating coating composition characterized in that the content of the silane coupling agent is 1 to 10 wt% with respect to the total of the poly-α-olefin and the silane coupling agent.

Here, R ₁ is a hydrogen or methyl group, and R ₂ is a linear alkyl group having 5 to 20 carbon atoms. A heat-dissipating coating comprising the heat-dissipating coating composition according to claim 1 and formed on the surface of a base material. The heat-dissipating coating according to claim 2 , wherein the thickness is 15 to 50 μm. The heat-dissipating coating according to claim 2 or 3 , wherein the base material is formed of a material containing aluminum. The heat-dissipating coating according to any one of claims 2 to 4 , wherein the content of the heat-dissipating filler formed from the inorganic particles is 0.1 wt% or less. The heat-dissipating coating according to any one of claims 2 to 5 , wherein the heat-dissipating filler formed from inorganic particles is not contained. A film forming method for forming a film on the surface of a base material.
The first step of applying a solution containing the composition represented by the following chemical formula (1) and a silane coupling agent to the surface of the base material, and
After the first step, the second step of heating the base material coated with the solution at 100 ° C. to 150 ° C. is included.
_{R 2} of the chemical formula (1) is a linear alkyl group having 10 to 15 carbon atoms.
A film forming method characterized in that the content of the silane coupling agent is 1 to 10 wt% with respect to the total of the poly-α-olefin and the silane coupling agent.

Here, R ₁ is a hydrogen or methyl group, and R ₂ is a linear alkyl group having 5 to 20 carbon atoms.

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